semi合集-English.pdf - 第3875页

SEMI F24-0697 © SEMI 1997, 2003 5 NOTICE: SEMI makes no warranties or representations as to the suitability o f the standards set forth herei n for any particul ar applicat ion. The determination of the suitability of th…

SEMI F24-0697 © SEMI 1997, 2003 4

RELATED INFORMATION 1

NOTES ON ASPIRATION EFFICIENCIES OF WALL TAP SAMPLE

PORTS

NOTICE: This related information is not an official part of SEMI F24 and is not intended to modify or supercede the official

standard. Determination of the suitability of the material is solely the responsibility of the user.

R1-1 Introduction

R1-1.1 Isokinetic sample probes are usually not

provided in speciality gas systems. Particle sampling is

usually performed using wall tap sample ports. Wall

tap sample ports are oriented 90° to the process line

flow as shown in Figure R1-1. Non-isokinetic flow into

the sample tube results from the 90° change in flow

direction. Additional deviation from isokinesis can

result from stream tube contraction or expansion when

the velocities U and v are not equal. The effects of

non-isokinetic flow on the measurement should be

checked. The particle sampling process should be

performed with an aspiration efficiency close to 1.

Process Line

v, C

To Sampling System

Wall Tap

U, Co, p

Figure R1-1

Schematic Diagram of Process Line and Wall Tap

Sample Port

R1-2 Variables

= Diameter of particle (cm)

= Intrinsic density of particle (g/cm

)

η = Dynamic viscosity of the gas (g/s-cm)

λo = Mean free path of the gas at atmospheric pressure

(cm)

p = Pressure of the gas (Pa)

= Atmospheric pressure (= 1 × 10

Pa)

D = Diameter of wall tap sample tube (cm)

U = Average velocity of the process line flow (cm/s)

v = Average velocity of the sample line flow (cm/s)

C* = Stokes-Cunningham slip correction factor

= Stokes number

R = Velocity ratio

Co = Particle concentration in the process line (cm

–3

)

C = Particle concentration in the sample line (cm

–3

)

R1-3 Calculations

R1-3.1 The Stokes-Cunningham slip correction factor

is calculated for particles in the size range of interest:

C* = 1 + 2.492

0. 84

−

435pd

/ p

Calculate the velocity ratio and Stokes number. The

intrinsic particle density may assume a worst case value

of 10 g/cm

=U/v

UC*

A wall tap sample port can be approximated as a

sampling probe oriented 90° to the flow. Calculate the

aspiration efficiency:

1 + 8S

1/2

Repeat the calculations for particle sizes in the range of

interest. When the aspiration efficiency is significantly

different from 1, the calculated efficiency should be

used to correct the measured particle concentration, C.

R1-4 References

Stevens, D. C. Review of Aspiration Coefficients of

Thin-Walled Sampling Nozzles. J. Aerosol Sci.,

17(4):729–743, 1986.

Vincent, J. H., D. C. Stevens, D. Mark, M. Marshall,

and T. A. Smith. On the Aspiration Characteristics of

Large-Diameter, Thin-Walled Aerosol Sampling Probes

at Yaw Orientations With Respect to the Wind. J.

Aerosol Sci., 17(2):211–224, 1986.

SEMI F24-0697 © SEMI 1997, 2003 5

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any particular application. The

determination of the suitability of the standard is solely

the responsibility of the user. Users are cautioned to

refer to manufacturer's instructions, product labels,

product data sheets, and other relevant literature,

respecting any materials or equipment mentioned

herein. These standards are subject to change without

notice.

By publication of this standard, Semiconductor

Equipment and Materials International (SEMI) takes no

position respecting the validity of any patent rights or

copyrights asserted in connection with any items

mentioned in this standard. Users of this standard are

expressly advised that determination of any such patent

rights or copyrights, and the risk of infringement of

such rights are entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI F25-0697 © SEMI 1997, 2003 1

SEMI F25-0697 (Reapproved 0303)

PARTICLE SPECIFICATION FOR GRADE 10/0.2 OXIDANT SPECIALTY

GASES

This specification was technically approved by the Global Gases Committee and is the direct responsibility of

the North American Gases Committee. Current edition approved by the North American Regional Standards

Committee on October 25, 2002. Initially available at www.semi.org December 2002; to be published March

2003. Originally published June 1997.

1 Purpose

1.1 The purpose of this document is to set a maximum

permissible particle concentration for 10/0.2 grade

oxidant specialty gases and to describe a reference

method for its verification.

2 Scope

2.1 This document applies only to oxidant gases

delivered through specialty gas systems at pressures up

to 8 × 10

Pa (8 atmospheres). This method is not

suitable for direct sampling from high pressure

cylinders at pressures above 8 × 10

Pa (8

atmospheres). This document applies only to the

following gas:

Oxygen (O

)

Nitrous Oxide (N

Nitrogen Trifluoride (NF

)

2.2 This standard does not purport to address safety

issues, if any, associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Referenced Standards

3.1 SEMI Standard

SEMI C6.2 — Particle Specification for Grade 20/0.02

Oxygen Delivered as Pipeline Gas

3.2 JIS Standard

JIS B 9921 — Japanese Industrial Standard (1989),

“Light Scattering Automatic Particle Counter”

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

1 Japanese Industrial Standards, Available through the Japanese

Standards Association, 1-24, Akasaka 4-Chome, Minato-ku, Tokyo

107-8440, Japan. Telephone: 81.3.3583.8005; Fax: 81.3.3586.2014

Website: http://www.jsa.or.jp

4 Terminology

4.1 Variables

= Volume of the i

sample interval of the system gas

= Volume of the i

sample interval of the background

= Concentration of particles observed in the i

sample o

interval of the system gas

= Concentration of particles observed in the i

sample o

interval of the background

= Number of sample intervals of the system gas

= Number of sample intervals of the background

Average observed concentration of counts in the

system gas sample

Average observed concentration of background counts

Calculated concentration of particles in the system gas

Standard deviation of

4.2 gas sample volume (V

, V

) — The volume of the

sample interval, expressed in standard liters at standard

conditions, 0°C (32°F) and 1 × 10

Pa (1 atmosphere)

pressure. Standard cubic feet (SCF) is defined at

21.1°C (70°F) and 1 × 10

Pa (1 atmosphere) pressure.

4.3 average observed concentration of counts

(

X ,

X ) — The average concentration of counts, i.e.:

4.4 calculated concentration of particles (

X ) — The

concentration of particles in the system gas obtained by

correcting the observed concentration in the system gas

for the observed concentration in the background, i.e.:

= X

− X

4.5 standard deviation (S

, S

) — A statistical

measure of the spread of the concentration of the counts

or particles. The first two are obtained from the

interval and average concentrations and the number of

intervals, i.e.: